Conventionally, in wireless communication between mobile stations and base stations, Transmission Power Control (TPC) is used as a technology for controlling the electrical power needed to transmit data from the mobile stations to the base stations.
With TPC, first, a base station receives data from a mobile station and then detects its reception level. The base station transmits a TPC value in accordance with the detected reception level back to the mobile station. Specifically, if the detected reception level is equal to or less than a predetermined value, the base station transmits an instruction to increase the electrical power by a given TPC value. In contrast, if the detected reception level is greater than a predetermined value, the base station transmits an instruction to decrease the electrical power by a given TPC value. A TPC value is transmitted for each frame. Specifically, the TPC is executed in units of one frame. With this TPC, a reception level in a base station can be controlled so that it is within an appropriate range.
Related-art example is described, for example, in Japanese Laid-open Patent Publication No. 2008-17009.
However, the content of an instruction represented by a TPC value may sometimes not accurately indicate the actual propagation environment status. For example, if an instruction to increase electrical power is given even though the actual propagation environment is satisfactory, excessive electrical power is consumed in the device on the transmission side. In contrast, if an instruction to reduce electrical power down is given even though the actual propagation environment is unsatisfactory, there may possibly sometimes be a case in which the transmitted data is not received or in which, even if the data is received, errors often occur. In this state, because the same data is repeatedly transmitted, electrical power consumption increases on the transmission side and the reception side and, furthermore, the resources used for the data transmission are consumed wastefully.